1. Field of the Invention
The present invention relates generally to the field of dump trucks. More specifically, the present invention discloses a method and device for holding the tailgate of a dump truck partially open to dispense material from the bed of the dump truck in a controlled manner.
2. Statement of the Problem
Dump trucks have been used for many years to transport and dispense materials (such as sand, road salt, gravel or dirt) from the rear of the bed of the dump truck through a tailgate. FIG. 1 is a rear perspective view of a conventional dump truck 10 with a bed 11 for transporting material. The tailgate 12 is typically pivotally attached by hinges at its upper corners to the rear side walls of the bed 11. The tailgate 12 completely closes the rear opening of the dump truck bed in its closed position, and two latch mechanisms 14 on either side of the rear of the dump truck engage two latch pins 13 that extend laterally outward from the lower edge of the tailgate 12 to secure the tailgate 12 in place. To open the tailgate 12, the operator releases the latch mechanisms 14, thereby allowing the tailgate 12 to freely pivot rearward about its upper hinges. Raising the truck bed 11 causes material in the bed 11 to slide rearward and exert pressure against the tailgate 12. This causes the tailgate 12 to pivot rearward and permits material to exit from the truck bed by flowing through the resulting opening between the bottom of the tailgate and rear end of the bed 11 of the truck 10.
The latch mechanisms 14 can typically be controlled by the operator from inside the cab of the truck 10 to release the tailgate 12. As illustrated in FIG. 1, the latch mechanism 14 usually includes a base attached to the rear of the truck bed 11 adjacent to the tailgate, and a hydraulically-actuated dog 15 for engaging one of the latch pins 13 extending from the tailgate 12. In the tail gate's closed position, the dog 15 draws and holds the latch pin 13 securely against the base of the latch mechanism 14. In the open position, the dog 15 is lifted upward to release the latch pin 13 from the base of the latch mechanism and thereby allow the tailgate 12 to pivot rearward.
Simply releasing the tailgate to swing freely open is acceptable in many fields of use, such as when the entire load is to be quickly dumped at a single location. However, this approach can be less than satisfactory in situations in which a generally even distribution of material is desired as the truck moves over a road or work area. In these cases, the tailgate 12 must be held in a partially open position to meter or control the flow of material (e.g., road salt or sand) from the truck bed 11 over time as the truck moves. One conventional approach to this problem has been to fasten chains 16 between side walls of the truck bed 11 and the tailgate 12, as shown in FIG. 1. The chains 16 limit the maximum opening of the tailgate 12 and are relatively easy to adjust. However, chains 16 can allow the tailgate 12 to pivot back toward the closed position, and thus chains have the disadvantage of not necessarily maintaining a uniform tailgate opening.
Therefore, a need exists for a method and device to securely hold the tailgate of a dump truck in a partially open position. Preferably, this improvement should be easy to use, inexpensive and suitable for use with a wide range of existing dump trucks.
The prior art in this field also includes a number of examples of devices to control the position of a dump truck's tailgate. For example, U.S. Pat. No. 7,591,513 (Morley) discloses a system for controlling the tailgate opening that uses a rigid connecting arm bolted to the tailgate. The body of the dump truck includes a control unit that catches the end piece of the connecting arm as the tailgate falls to the closed position. The operator can select any of a number of opening positions for the tailgate.
U.S. Pat. No. 6,302,491 (Anderson) discloses another example of a control system for controlling the position of a dump truck tailgate. An hydraulic actuator controls the position of an L-shaped latch member that regulates the degree of opening of the tailgate. U.S. Pat. No. 3,572,837 (Lackey) shows a similar control system operated by rods, cables and pulleys. However, such systems have the disadvantages of significant cost and complexity, and would require substantial modifications to existing dump trucks.
3. Solution to the Problem
The present invention provides a method and device for holding the tailgate of a dump truck in a partially open position by means of a removable post having openings at its ends for engaging the latch pin extending from the tailgate and the latch on the rear of the dump truck. The dog of the latch is then inserted into an opening in the proximal end of the post to secure the post to the latch.
This approach allows the present invention to be used in conjunction with a wide variety of existing dump trunks without requiring modifications. In addition, the present invention can be manufactured at relatively low cost, and can be quickly installed and removed in the field.